Useful Kotlin extensions

Extensions.kt

fun <T> MutableList<T>.addOrRemove(item: T) {
    if (this.contains(item)) {
        this.remove(item)
    } else {
        this.add(item)
    }
}

fun <T> MutableList<T>.findIndex(predicate: (T) -> Boolean): Int {
    val item = this.find(predicate)
    return this.indexOf(item)
}

fun <R> CoroutineScope.asyncTask(
    onPreExecute: () -> Unit,
    doInBackground: () -> R,
    onPostExecute: (R) -> Unit
) = launch {
    onPreExecute()
    val result = withContext(Dispatchers.IO) {
        doInBackground()
    }
    onPostExecute(result)
}